It is becoming more common to replace a missing tooth with a prosthetic tooth that is placed upon and attached to a dental implant. Dental implants are often comprised of metal and metal alloys, including titanium (Ti) and titanium alloys. The dental implant serves as an artificial root that integrates with the gingiva and the bone tissue of the mouth.
For the dental implant to function successfully, sufficient osseointegration is required. In other words, a direct chemical bond between the implant and the bone must be formed and retained. Osseointegration materials may be incorporated onto the surface of the implant to help enhance the osseointegration process. Non-limiting examples of osseointegration materials include calcium phosphate ceramic materials such as hydroxyapatite (HA), which is particularly chemically stable and osseoconductive.
To provide sufficient long-term behavior of an implant having an osseointegration compound on the surface, there must be a sufficient bond strength between the implant and the compound. Moreover, the compound is desirably sufficiently biostable such that the rate of dissolution of the compound is low.
Several existing techniques involve forming a generally thin (e.g., generally less than 10 microns) coating of HA, other calcium phosphates, or other osseointegration compounds for improving the bond strength of the coating to the implant. Plasma spraying and sputtering are two major techniques that have been used to deposit, for example, HA onto an implant. The dissolution rate of HA for these processes, however, may be undesirably high. Moreover, the interface of the HA and the implant is prone to fracture, which is often caused by poor adherence of the HA to the metal implant.
U.S. Pat. App. Pub. No. 2004/0249472 discloses a method of coating an implant with nanoscale calcium phosphate (e.g., HA). Although effective, the disclosed process is hazardous in that it requires utilizing highly flammable chemicals and produces hazardous byproducts (e.g., waste). Moreover, the process is inefficient because it requires that the implant first be coated with a layer comprising alkoxides or tri-functional silanes (i.e., aminopropyltriethoxysilane) to form a positively charged surface of the implant. A second coating layer comprising negatively charged HA nanoparticles is then formed on the first coating layer.
The present invention is directed to an improved implant having discrete nanocrystalline calcium phosphate (e.g., HA) deposited on the implant surface and methods of forming the same.